White House won't say Manchin-Toomey is doomed

4/17/13 1:02 PM EDT

President Obama and the rest of the White House are still working to get the Senate to pass gun legislation, press secretary Jay Carney said Wednesday, just as an undecided Democratic senator announced that she plans to vote against the bill.

"Everybody in the White House is working on this issue from the president on down," Carney said during his daily briefing. Later, he added: "Hopefully there'll be reason to be pleased by the outcome. If that's not the case, we'll assess that."

Though public counts suggest that the background checks amendment up for consideration Wednesday won't get the 60 votes needed, Carney urged caution, suggesting lawmakers might change their votes. "I still think each senator has to think for himself or herself" on what he or she ulitmately vote for, he said. "What they tell the press and what they tweet is not the same as how they vote."

"I won't give post-game analysis before the game is over," he said more than once.

Carney spoke as Sen. Heidi Heitkamp (D-N.D.) said she will vote against the Manchin-Toomey amendment. "I’ve thought long and hard about this, I’ve taken the tough meetings, and I’ve heard overwhelmingly from the people of North Dakota; and at the end of the day my duty is to listen to and represent the people of North Dakota," she said. Earlier Wednesday, Sen. Kelly Ayotte (R-N.H.) said she would also be voting against the amendment, bringing the total number opposed to 42.

But Carney wouldn't concede that the Manchin-Toomey amendment was bound to fall short. "The president believes that every senator ought to support common sense legislation to reduce gun violence, 100 of them," he said. Tighter background checks "should garner the support in the Senate that it has in the country."

The senators who say they will vote against the amendment "represent the very people who have said overwhelmingly that they want this done," Carney said said. Though there may be Democrats opposed to it, "make no mistake, on this matter … the overwhelming number of Democrats support it and the overwhelming number of Republicans oppose it. And that is a shame."